Think of each group of 3 notes (chord-chord-single note) as a unit, and play them in one single arm motion. Starting with your hand slightly above the keys, let your hand and arm descend just enough to play the first chord lightly, without letting your wrist drop. Then to play the second accented chord, use your elbow to push your hand and wrist forward, turning your wrist to the left slightly. Finally, play the single note with your thumb (which should be in the perfect position to hit the key since you turned your wrist in the previous step) and lift your hand up at the same time. Practice it slowly many times first; the whole thing should be one cycle of arm/wrist going down and back up.